I'm trying to execute a command for each line coming from a cat command. I'm basing this on sample code I got from a vendor.
Here's the script:
for tbl in 'cat /tmp/tables'
do
echo $tbl
done
So I was expecting the output to be each line in the file. Instead I'm getting this:
cat
/tmp/tables
That's obviously not what I wanted.
I'm going to replace the echo with an actual command that interfaces with a database.
Any help in straightening this out would be greatly appreciated.
You are using the wrong type of quotes.
You need to use the back-quotes rather than the single quote to make the argument being a program running and piping out the content to the forloop.
for tbl in `cat /tmp/tables`
do
echo "$tbl"
done
Also for better readability (if you are using bash), you can write it as
for tbl in $(cat /tmp/tables)
do
echo "$tbl"
done
If your expectations are to get each line (The for-loops above will give you each word), then you may be better off using xargs, like this
cat /tmp/tables | xargs -L1 echo
or as a loop
cat /tmp/tables | while read line; do echo "$line"; done
The single quotes should be backticks:
for tbl in `cat /etc/tables`
Although, this will not get you output/input by line, but by word. To process line by line, you should try something like:
cat /etc/tables | while read line
echo $line
done
With while loop:
while read line
do
echo "$line"
done < "file"
You can do a lot of parsing in bash by redefining the IFS (Input Field Seperator), for example
IFS="\t\n" # You must use double quotes for escape sequences.
for tbl in `cat /tmp/tables`
do
echo "$tbl"
done
"\t\n" Otherwise, single quotes will literally preserve the meaning of '\', 't', 'n.